Caption: Lift-off the space shuttle Challenger on the ill- fated mission 51-L. A puff of black smoke can be seen at the base of the solid rocket booster where an O-ring seal failed on ignition. Seventy-three seconds after lift-off the shuttle exploded killing all seven crew members. The freezing temperatures experienced prior to the launch are thought to have caused the failure of the O-ring. Challenger was launched from launch pad 39B at Kennedy Space Center, Florida, at 11.38am on January 28th 1986.